Introduction. Retinopathy of prematurity (ROP) is an alteration in the development of the vessels of the retina with an incidence ranging from 12 to 78%. We undertook this study to determine risk factors associated with ROP in a group of premature infants. Methods. This is a retrospective and comparative study in search of risk factors of ROP, reviewing the records of infants weighing < 1500 g or gestational age ≤ 30 weeks admitted to the Neonatology Department. We carried out an ophthalmoscopy study at 4 weeks of age and then weekly until hospital discharge. We compared the group with and without retinopathy. Variables registered were birth weight, gestational age, oxygen exposure, total parenteral nutrition, antibiotics, lung disease, severe perinatal asphyxia, peri-intraventricular hemorrhage, septicemia, hyperbilirubinemia, bronchopulmonary dysplasia and red blood cell transfusion. Comparative analysis was carried out by ANOVA and logistic regression by calculating odds ratios (OR) and 95% confidence interval (95% CI). Results. We reviewed 112 infants with ROP and 95 infants without ROP. According to gender ratio, birth weight, gestational age, mechanical ventilation and days with ventilation, there was no significant difference. Risk factors were antibiotics (OR 2.36, 95% CI 1.22-4.59)), erythrocyte transfusion (OR 2.99, 95% CI 1.50-5.99), total parenteral nutrition (OR 3.20, 95% CI 1.63-6.25), and sepsis (OR 1.83, 95% CI 1.01-3.34). Conclusions. ROP was present mainly in infants with very serious disease and risk factors were antibiotics, erythrocyte transfusion, total parenteral nutrition and sepsis.